会话跟踪技术（Cookie、Session）

创始人

2024-01-17 04:35:00

0次

一、Cookie

客户端会话跟踪技术，将数据保存到客户端，以后每次请求都携带Cookie数据进行访问

Cookie的基本使用

发送Cookie

创建Cookie对象，设置数据

 Cookie cookie=new  Cookie("key","value");

发送Cookie到客户端：使用response对象

response.addCookie(cookie);

一、添加pom依赖

    javax.servletjavax.servlet-api4.0.1providedjavax.servlet.jspjsp-api2.2providedjstljstl1.2taglibsstandard1.1.2

二、创建Servlet

package com.GY;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;@WebServlet(name = "AServlet", value = "/AServlet")
public class AServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// 发送Cookie// 1.创建Cookie对象Cookie cookie=new Cookie("username","GY");// 2.发送Cookieresponse.addCookie(cookie);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}
}

三、启动服务器，在浏览器中查看Cookie数据

在这里插入图片描述数据成功写入客户端！！！

获取Cookie

获取客户端携带的所有Cookie，使用request对象

 Cookie[]  cookies=request.getCookies();

遍历数组，获取每一个Cookie对象：for
使用Cookie对象方法获取数据

cookie.getName();

cookie.getValue();

一、创建Servlet

package com.GY.cookie;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;@WebServlet(name = "BServlet", value = "/BServlet")
public class BServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// 获取Cookie// 1.获取Cookie数组Cookie[] cookies = request.getCookies();// 2.遍历数组for (Cookie cookie : cookies) {// 3.获取数据String name = cookie.getName();if ("username".equals(name)) {String value = cookie.getValue();System.out.println(name+":"+value);break;}}}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}
}

二、启动服务器
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成功访问到Cookie中的数据！！！

Cookie原理

Cookie的实现是基于HTTP协议的
●  响应头: set-cookie
●  请求头: cookie

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Cookie使用细节

● Cookie存活时间默认情况下，Cookie存储在浏览器内存中，当浏览器关闭，内存释放，则Cookie被销毁setMaxAge(int seconds):设置Cookie存活时间1.正数: 将Cookie写入浏览器所在电脑的硬盘,持久化存储。到时间自动删除（不会随浏览器的关闭而被销毁）2.负数: 默认值,Cookie在当前浏览器内存中,当浏览器关闭,则Cookie被销毁3.零: 删除对应Cookie● Cookie存储中文Cookie不能直接存储中文如需要存储,则需要进行转码: URL编码

① Cookie存活时间

// 设置存活时间   ,  一周(七天)cookie.setMaxAge(60*60*24*7);

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② Cookie存储中文
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URL编码

package com.GY.cookie;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.net.URLEncoder;@WebServlet(name = "AServlet", value = "/AServlet")
public class AServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// 发送Cookie// 1.创建Cookie对象String value="张三";// URl编码value=URLEncoder.encode(value,"UTF-8");System.out.println("存储数据:"+value);Cookie cookie=new Cookie("username",value);// 设置存活时间   ,  一周(七天)cookie.setMaxAge(60*60*24*7);// 2.发送Cookieresponse.addCookie(cookie);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}
}

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URL解码

package com.GY.cookie;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URLDecoder;@WebServlet(name = "BServlet", value = "/BServlet")
public class BServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// 获取Cookie// 1.获取Cookie数组Cookie[] cookies = request.getCookies();// 2.遍历数组for (Cookie cookie : cookies) {// 3.获取数据String name = cookie.getName();if("username".equals(name)) {String value = cookie.getValue();// URL解码value = URLDecoder.decode(value, "UTF-8");System.out.println(name + ":" + value);break;}}}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}
}

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成功获取中文数据！！！

二、Session

服务端会话跟踪技术，将数据保存到服务端
JavaEE提供HttpSession接口,来实现一次会话的多次请求间数据共享功能

Session基本使用

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获取Session对象

 HttpSession  session=request.getSession();

Session的对象功能

void setAttribute（String  name,Object  o）:  存储数据到Session域中
Object  getAttribute（String  name）:  根据key,获取值
void  removeAttribute（String  name):  根据key，删除该键值对

一、创建Servlet（存储数据）

package com.GY.session;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.Enumeration;@WebServlet(name = "A1Servlet", value = "/A1Servlet")
public class A1Servlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//  1.获取Session对象HttpSession session = request.getSession();//  2.存储数据session.setAttribute("username","GY");}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}
}

二、创建Servlet（获取数据）

package com.GY.session;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;@WebServlet(name = "B1Servlet", value = "/B1Servlet")
public class B1Servlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//  从Session中获取数据//  1.获取对应的Session对象HttpSession session = request.getSession();//  2. 获取数据Object username = session.getAttribute("username");System.out.println(username);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}
}

二、启动服务器
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成功获取数据！！！

Session原理

Session的实现是基于Cookie的
在这里插入图片描述

Session使用细节

● Session钝化、活化服务器重启后，Session中的数据是否还在？钝化: 在服务器正常关闭后,Tomcat会自动将Session数据写入硬盘的文件中 活化: 再次启动服务器后，从文件中加载数据到Session中● Session销毁默认情况下,无操作，30分钟自动销毁（分钟）【可在web.xml中配置】30调用Session对象的invalidate()方法

三、小结

Cookie和Session都是来完成一次会话内多次请求间数据共享的
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区别：

      ●   存储位置: Cookie是将数据存储在客户端,Session是将数据存储在服务端●   安全性:  Cookie不安全,Session安全●   数据大小: Cookie最大3kb,Session无大小限制●  存储时间: Cookie可以长期存储,Session默认30分钟●  服务器性能:  Cookie不占服务资源,Session占用服务资源

【一般Cookie保证用户未登录的情况下身份识别，Session一般保存用户登录后的数据；不同的需求需具体分析后选择】

四、登录注册案例

需求说明：1. 完成用户登录功能，如果用户勾选 “记住用户” ，则下次访问登录页面，自动填充用户名密码3. 完成注册功能，并实现验证码验证

数据库表数据——user表
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数据库数据——tb_brand表

项目资源
链接：https://pan.baidu.com/s/1CVGnG3bHGdq5dSGHBDin9g
提取码：GY66

Mybatis配置文件

Dao层——BrandMapper

import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.ResultMap;
import org.apache.ibatis.annotations.Select;
import java.util.List;public interface BrandMapper {@Select("select * from tb_brand")@ResultMap("brandResultMap")List selectAll();
}

Dao层——UserMapper

package com.GY.mapper;import com.GY.pojo.User;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;public interface UserMapper {@Select("select * from user where username = #{username} and password = #{password}")User select(@Param("username") String username,@Param("password")  String password);
}

Service层——UserService

package com.GY.service;import com.GY.mapper.UserMapper;
import com.GY.pojo.User;
import com.GY.util.SqlSessionFactoryUtils;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;public class UserService {SqlSessionFactory factory = SqlSessionFactoryUtils.getSqlSessionFactory();public User login(String username,String password){//2. 获取SqlSessionSqlSession sqlSession = factory.openSession();//3. 获取UserMapperUserMapper mapper = sqlSession.getMapper(UserMapper.class);//4. 调用方法User user = mapper.select(username, password);//释放资源sqlSession.close();return  user;}
}

Service层——BrandService

package com.GY.service;import com.GY.mapper.BrandMapper;
import com.GY.pojo.Brand;
import com.GY.util.SqlSessionFactoryUtils;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;import java.util.List;public class BrandService {SqlSessionFactory factory = SqlSessionFactoryUtils.getSqlSessionFactory();public List selectAll(){//调用BrandMapper.selectAll()//2. 获取SqlSessionSqlSession sqlSession = factory.openSession();//3. 获取BrandMapperBrandMapper mapper = sqlSession.getMapper(BrandMapper.class);//4. 调用方法List brands = mapper.selectAll();sqlSession.close();return brands;}
}

Web层——LoginServlet类

package com.GY.web;import com.GY.pojo.User;
import com.GY.service.UserService;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {private UserService service = new UserService();@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//1. 获取用户名和密码String username = request.getParameter("username");String password = request.getParameter("password");//2. 调用service查询User user = service.login(username, password);//3. 判断if(user != null){//登录成功，跳转到查询所有的BrandServlet（重定向）// 将登录成功后的User对象，存储到SessionHttpSession session = request.getSession();session.setAttribute("user",user);String contextPath = request.getContextPath();response.sendRedirect("/selectAllServlet");}else {// 登录失败,// 存储错误信息到requestrequest.setAttribute("login_msg","用户名或密码错误");// 跳转到login.jsprequest.getRequestDispatcher("/login.jsp").forward(request,response);}}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doGet(request, response);}
}

Web层——SelectAllServlet 类

package com.GY.web;import com.GY.pojo.Brand;
import com.GY.service.BrandService;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.List;@WebServlet("/selectAllServlet")
public class SelectAllServlet extends HttpServlet {private  BrandService service = new BrandService();@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//1. 调用BrandService完成查询List brands = service.selectAll();//2. 存入request域中request.setAttribute("brands",brands);//3. 转发到brand.jsp（请求转发）request.getRequestDispatcher("/brand.jsp").forward(request,response);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doGet(request, response);}
}

效果展示
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